1. Field of the Invention
The invention relates to a wire for use in electrical cables with fire-resistant insulation of its inner conductor.
2. Description of the Related Art
Such a wire has been described, for example, in the DE 197 17 645 C2 with regard to the technical background and also with regard to the design of correspondingly fire-resistant compositions, thus ensuring insulation and functional integrity of the wire or a cable based on it in case of a fire. Where wires of this kind are employed in electrical cables a layer manufactured from a correspondingly fire-resistant composition is normally applied to the conductor, which then forms the basis for further sheathing of the wire consisting of further insulation layers and/or layers from a respectively suitable sheathing material. The individual wires are normally grouped together to form multi-wire stranded cores which can be used for the manufacture of electrical cables with improved behaviour in case of fire as regards their insulation and functional integrity.
Further, an optical cable with an optical wave guide is known from DE 195 17 392 A1 in whose cable sheath is provided an inner protective layer from a heat-resistant material such as glass and/or ceramic and/or mica, such that after flaming it forms a tube-shaped structure for protecting the optical wave guide, wherein a further outer sheathing layer consists of a fire-retarding material, in particular a FRNC material. Such a construction of the sheath may not be sufficient if the stress in case of a fire is very high.